The effects of temperature （0-500°C） on the compressive strength,hardness,average relative density,and microstructure of Ti6Al4V powder green compacts prepared by magnetic pulse compaction were investigated.The...The effects of temperature （0-500°C） on the compressive strength,hardness,average relative density,and microstructure of Ti6Al4V powder green compacts prepared by magnetic pulse compaction were investigated.The results show that with increasing heating temperature,the compressive strength first increases and then decreases with the maximum value of 976.74 MPa at 400°C.The average relative density and hardness constantly increase,and their values reach 96.11% and HRA 69.8 at 500°C,respectively.The increase of partial welding is found among the junctions of particles inside the compacts; there is no obvious grain growth inside the compacts within the temperature range.展开更多
This paper is devoted to the study of frequency effects on hardness profile of AISI 4340 spline shaft heat-treated by induction through an extensive 3D finite element method simulation and structured experimental inve...This paper is devoted to the study of frequency effects on hardness profile of AISI 4340 spline shaft heat-treated by induction through an extensive 3D finite element method simulation and structured experimental investigation. Based on coupled electromagnetic and thermal fields analysis, the 3D model is used to estimate the temperature distribution and the hardness profile. The proposed study examines the hardening process parameters, such as frequency, induced current density and heating time, known to have an influence on hardened surface and builds the simulation model step by step. The established model can provide not only an accurate prediction of temperature distribution and hardness profile but also a comprehensive analysis of machine parameters effects, especially the frequency. The numerical results achieved by this model are good and present a great agreement to the experimental data.展开更多
Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was...Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was the main diffusing species migrating from the cathode to the anode. The electromigration force and Joule heating took on the main driving forces for Bi diffusion and migration. In addition, two appearance types of Bi layers, planar-type and groove-type, were found during current stressing. The morphology and thickness of Bi layers were affected by current density and current stressing time.展开更多
Ruthenium has been hailed as a competitive alternative for platinum toward hydrogen evolution reaction(HER),a critical process in electrochemical water splitting.In this study,we successfully prepare metallic Ru nanop...Ruthenium has been hailed as a competitive alternative for platinum toward hydrogen evolution reaction(HER),a critical process in electrochemical water splitting.In this study,we successfully prepare metallic Ru nanoparticles supported on carbon paper by utilizing a novel magnetic induction heating(MIH)method.The samples are obtained within seconds,featuring a Cl-enriched surface that is unattainable via conventional thermal annealing.The best sample within the series shows a remarkable HER activity in both acidic and alkaline media with an overpotential of only-23 and-12 mV to reach the current density of 10 mA/cm^(2),highly comparable to that of the Pt/C benchmark.Theoretical studies based on density functional theory show that the excellent electrocatalytic activity is accounted by the surface metal-Cl species that facilitate charge transfer and downshift the d-band center.Results from this study highlight the unique advantages of MIH in rapid sample preparation,where residual anion ligands play a critical role in manipulating the electronic properties of the metal surfaces and the eventual electrocatalytic activity.展开更多
Observations are presented of the phenomenon of the enhancement in electron density and temperature that is caused by a powerful pump wave at a frequency near the fifth gyrofrequency. The observations show that the ap...Observations are presented of the phenomenon of the enhancement in electron density and temperature that is caused by a powerful pump wave at a frequency near the fifth gyrofrequency. The observations show that the apparent enhancement in electron density extending over a wide altitude range and the enhancement in electron temperature around the reflection altitude occur as a function of pump frequency. Additionally, the plasma line spectra show unusual behavior as a function of pump frequency. In conclusion, the upper hybrid wave resonance excited by the pump wave plays a dominating role and leads to the enhancement in electron temperature at the upper hybrid altitude. The phenomenon of apparent enhancement in electron density does not correspond to the true enhancement in electron density, this may be due to some mechanism that preferentially involves the plasma transport process and leads to the strong backscatter of radar wave along the magnetic line, which remains to be determined.展开更多
Science is the basis of the country’s development and wealth. In particular, it is necessary to effectively use advanced scientific developments and technical achievements in order to strengthen the economy in the pe...Science is the basis of the country’s development and wealth. In particular, it is necessary to effectively use advanced scientific developments and technical achievements in order to strengthen the economy in the period when the desire for innovation in all fields is still growing. In theoretical-experimental Scientific Research work, both theoretical and experimental results are achieved, and it is more useful to withstand more theoretical-experimental loads for a longer period of time. The occurrences in the production process of natural wool fiber technologists are a complex of physical and mechanical phenomena, which can be used only by the modern achievements of science and technology. In most cases, the parameter relationship with the factors influencing the technological process or the object can open a curve without any other things.展开更多
The observation of ultra-high frequency radar during an ionospheric heating experiment carried out at TromsФ site of European Incoherent Scatter Scientific Association, Norway, is analyzed. When pump is operating sli...The observation of ultra-high frequency radar during an ionospheric heating experiment carried out at TromsФ site of European Incoherent Scatter Scientific Association, Norway, is analyzed. When pump is operating slightly above the fifth electron gyrofrequency, some strong enhancements in radar echo and electron density occur in a wide altitude range and are in sync with the shifting and spread of plasma line around the reflection altitude, which may be due to the focusing or collimating of radar wave by irregularities. While some strong enhancements in electron density and radar echo around the reflection altitude do not correspond to the true increase in electron density, but due to the enhanced ion acoustic wave by parametric decay instability and oscillation two stream instability. In addition, the different heating rates and cooling rates at the pump frequencies below, around and above fifth gyrofrequency respectively result in the dependence of the enhancements in electron temperature on the pump frequency.展开更多
Ion Bernstein waves （IBWs） have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency （27 MHz and 30 MHz） was carried...Ion Bernstein waves （IBWs） have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency （27 MHz and 30 MHz） was carried out on HT-7 superconducting tokamak in recent experiments. At a frequency of 30 MHz, ne peaked and Ha dropped have been pervasively observed, Tp was improved by a factor of 2 - 4, and Te increased by a factor of 1 - 1.5. An obvious confinement of particle was observed during the IBW pulse. At 27MHz, both global and localized electron heating were observed depending on the location of the ion resonant layer by changing Bt. Central electron heating effect was obtained in the global heating mode and electron temperature strongly increased near the 2 ΩD resonant layer for localized heating mode.展开更多
Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption prope...Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 ＆#176;C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.展开更多
文摘The effects of temperature （0-500°C） on the compressive strength,hardness,average relative density,and microstructure of Ti6Al4V powder green compacts prepared by magnetic pulse compaction were investigated.The results show that with increasing heating temperature,the compressive strength first increases and then decreases with the maximum value of 976.74 MPa at 400°C.The average relative density and hardness constantly increase,and their values reach 96.11% and HRA 69.8 at 500°C,respectively.The increase of partial welding is found among the junctions of particles inside the compacts; there is no obvious grain growth inside the compacts within the temperature range.
文摘This paper is devoted to the study of frequency effects on hardness profile of AISI 4340 spline shaft heat-treated by induction through an extensive 3D finite element method simulation and structured experimental investigation. Based on coupled electromagnetic and thermal fields analysis, the 3D model is used to estimate the temperature distribution and the hardness profile. The proposed study examines the hardening process parameters, such as frequency, induced current density and heating time, known to have an influence on hardened surface and builds the simulation model step by step. The established model can provide not only an accurate prediction of temperature distribution and hardness profile but also a comprehensive analysis of machine parameters effects, especially the frequency. The numerical results achieved by this model are good and present a great agreement to the experimental data.
基金supported by the China Postdoctoral Science Foundation (No. 20100480250)the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education(No. KZ200910005004)
文摘Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was the main diffusing species migrating from the cathode to the anode. The electromigration force and Joule heating took on the main driving forces for Bi diffusion and migration. In addition, two appearance types of Bi layers, planar-type and groove-type, were found during current stressing. The morphology and thickness of Bi layers were affected by current density and current stressing time.
基金National Science Foundation,Grant/Award Numbers:CHE-1900235,CHE-2003685Office of Science,Office of Basic Energy Sciences,of the U.S.Department of Energy,Grant/Award Number:DE-AC02-05CH11231+3 种基金U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Grant/Award Number:DE-AC02-76SF00515NSF MRI program,Grant/Award Number:AST-1828315Grant-in-Aid of Research,Grant/Award Number:G20211001-639National Academy of Sciences,administered by Sigma Xi,The Scientific Research Society。
文摘Ruthenium has been hailed as a competitive alternative for platinum toward hydrogen evolution reaction(HER),a critical process in electrochemical water splitting.In this study,we successfully prepare metallic Ru nanoparticles supported on carbon paper by utilizing a novel magnetic induction heating(MIH)method.The samples are obtained within seconds,featuring a Cl-enriched surface that is unattainable via conventional thermal annealing.The best sample within the series shows a remarkable HER activity in both acidic and alkaline media with an overpotential of only-23 and-12 mV to reach the current density of 10 mA/cm^(2),highly comparable to that of the Pt/C benchmark.Theoretical studies based on density functional theory show that the excellent electrocatalytic activity is accounted by the surface metal-Cl species that facilitate charge transfer and downshift the d-band center.Results from this study highlight the unique advantages of MIH in rapid sample preparation,where residual anion ligands play a critical role in manipulating the electronic properties of the metal surfaces and the eventual electrocatalytic activity.
基金supported by National Natural Science Foundation of China(No.40831062)
文摘Observations are presented of the phenomenon of the enhancement in electron density and temperature that is caused by a powerful pump wave at a frequency near the fifth gyrofrequency. The observations show that the apparent enhancement in electron density extending over a wide altitude range and the enhancement in electron temperature around the reflection altitude occur as a function of pump frequency. Additionally, the plasma line spectra show unusual behavior as a function of pump frequency. In conclusion, the upper hybrid wave resonance excited by the pump wave plays a dominating role and leads to the enhancement in electron temperature at the upper hybrid altitude. The phenomenon of apparent enhancement in electron density does not correspond to the true enhancement in electron density, this may be due to some mechanism that preferentially involves the plasma transport process and leads to the strong backscatter of radar wave along the magnetic line, which remains to be determined.
文摘Science is the basis of the country’s development and wealth. In particular, it is necessary to effectively use advanced scientific developments and technical achievements in order to strengthen the economy in the period when the desire for innovation in all fields is still growing. In theoretical-experimental Scientific Research work, both theoretical and experimental results are achieved, and it is more useful to withstand more theoretical-experimental loads for a longer period of time. The occurrences in the production process of natural wool fiber technologists are a complex of physical and mechanical phenomena, which can be used only by the modern achievements of science and technology. In most cases, the parameter relationship with the factors influencing the technological process or the object can open a curve without any other things.
文摘The observation of ultra-high frequency radar during an ionospheric heating experiment carried out at TromsФ site of European Incoherent Scatter Scientific Association, Norway, is analyzed. When pump is operating slightly above the fifth electron gyrofrequency, some strong enhancements in radar echo and electron density occur in a wide altitude range and are in sync with the shifting and spread of plasma line around the reflection altitude, which may be due to the focusing or collimating of radar wave by irregularities. While some strong enhancements in electron density and radar echo around the reflection altitude do not correspond to the true increase in electron density, but due to the enhanced ion acoustic wave by parametric decay instability and oscillation two stream instability. In addition, the different heating rates and cooling rates at the pump frequencies below, around and above fifth gyrofrequency respectively result in the dependence of the enhancements in electron temperature on the pump frequency.
基金The project supported by the Meg-science Engineering Project of the Chinese Academy of Sciences
文摘Ion Bernstein waves （IBWs） have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency （27 MHz and 30 MHz） was carried out on HT-7 superconducting tokamak in recent experiments. At a frequency of 30 MHz, ne peaked and Ha dropped have been pervasively observed, Tp was improved by a factor of 2 - 4, and Te increased by a factor of 1 - 1.5. An obvious confinement of particle was observed during the IBW pulse. At 27MHz, both global and localized electron heating were observed depending on the location of the ion resonant layer by changing Bt. Central electron heating effect was obtained in the global heating mode and electron temperature strongly increased near the 2 ΩD resonant layer for localized heating mode.
基金Project(51104073)supported by the National Natural Science Foundation of ChinaProject(2014CB643404)supported by the National Basic Research Program of China+1 种基金Project(2013AA064003)supported by the Hi-tech Research and Development Program of ChinaProject(2012HB008)supported by the Yunnan Provincial Young Academic Technology Leader Reserve Talents,China
文摘Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 ＆#176;C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.
